using Class<?> to represent an interface - class

Question

I hope the title accurately represents what I'm asking here. For my assignment here, I have a Speakerphone object, which is a singleton, and two interfaces, Listener and Talker with which Speakerphone needs to communicate.
There are two shoutMessage methods, the second of which takes a Class object as a parameter. Here's where I'm confused - I don't know if the "Class object" in the instructions is referring to the Listener interface, or the Speakerphone object. Can anyone tell me if the code in this method is correct, based on the instructions here?
public class Speakerphone extends Object {
private static Speakerphone sSpeaker = null;
private static HashSet<Listener> mListener = new HashSet<Listener>();
private static HashSet<Talker> mTalker = new HashSet<Talker>();
private Speakerphone() {
}
/*
* get
*
* #return the singleton instance of Speakerphone (Speakerphone)
*/
/************************************************
* ASSIGNMENT:
* Implement the get method
/************************************************/
public static Speakerphone get(){
if (sSpeaker == null){
sSpeaker = new Speakerphone();
}
return sSpeaker;
}
/*
* shoutMessage
*
* Sends the message to all of the Listeners tracked by Speakerphone
*
* #param talker a Talker whose message will be sent (Talker)
* #return nothing
*/
/************************************************
* ASSIGNMENT:
* Implement the shoutMessage method
/************************************************/
public void shoutMessage(Talker talker){
Iterator<Talker> talkIterator = mTalker.iterator();
while(talkIterator.hasNext())
talkIterator.next().getMessage();
}
/*
* shoutMessage
*
* Sends the message to all of the Listeners which are instances of
* the cls parameter
*
* #param talker a Talker whose message will be sent (Talker)
* #param cls a Class object representing the type which the Listener
* should extend from in order to receive the message (Class)
* #return nothing
*
* HINT: see Class.isAssignableFrom()
* http://docs.oracle.com/javase/7/docs/api/java/lang/Class.html#isAssignableFrom(java.lang.Class)
*/
/************************************************
* ASSIGNMENT:
* Implement the shoutMessage method
/************************************************/
public void shoutMessage(Talker talker, Class<?> cls){
if (Listener.class.isAssignableFrom(cls)){
Iterator<Talker> talkIterator = mTalker.iterator();
while(talkIterator.hasNext())
talkIterator.next().getMessage();
}
}
}

Answer 1

So, the class parameter in the shoutMessage method appears to be there so you can select out only listeners of a certain type. Class in Java is an object that describes a data type - a meta of meta so to speak.
Based on the comments in the code it looks like your shoutMessage method might be doing the opposite of what you want. Here's what I think it needs to do (based on the comments of the method):
Iterate through all of the listeners in your mListener HashSet. For each listener in the HashSet, do the following
As you iterate through, use Listener.class.isAssignableFrom to determine if the current listener is of class cls.
If it is of the type cls then call talker.getMessage() and pass that message to the current listener (by calling "receiveMessage" or "on" or whatever function is defined in your Listener interface).
If it is not of the type cls then ignore.